The present invention relates to an improved process for the preparation of polyalkylphenoxyaminoalkanes. More particularly, this invention relates to a process for the preparation of polyalkylphenoxyaminoalkanes which comprises the aminoethylation of a polyalkylphenol compound with 2-oxazolidinone or a derivative thereof in the presence of an alcohol.
Polyalkylphenoxyaminoalkanes are known fuel additives useful in the prevention and control of engine deposits. U.S. Pat. Nos. 5,669,939 and 5,851,242 describes a process for preparing these compounds. The process involves initially hydroxylating a polyalkylphenol with an alkylene carbonate in the presence of a catalytic amount of an alkali metal hydride or hydroxide, or alkali metal salt, to provide a polyalkylphenoxyalkanol which is subsequently reacted with an appropriate amine to provide the desired polyalkylphenoxyaminoalkane.
2-oxazolidinones or derivatives thereof are well described. For example, Martin E. Dyen and Daniel Swern, Chemistry Reviews (1967), pages 197-246 describes 2-oxazolidinones in detail. The use of 2-oxazolidinones or derivatives thereof in the aminoethylation of phenols is well known in the art.
U.S. Pat. No. 4,381,401 discloses the reaction of 2-oxazolidinone or N-substituted derivatives thereof with aromatic amine hydrochlorides at elevated temperatures to produce 1,2-ethanediamines. The 1,2-ethanediamines produced are an important class of materials which are useful as intermediates for the production of pharmaceuticals, photographic chemicals and other compositions.
Japanese Patent Publication No. JP 2592732 B2 discloses a method of producing phenoxyethylamines by reacting, under base conditions, low molecular weight phenols and 2-oxazolidinone. Phenoxyethylamines are important raw materials for pharmaceuticals and pesticides.
German Patent Publication DE 19711004 A1 discloses the use of 2-oxazolidinone to prepare phenoxyaminoalkanes from low molecular weight phenols. 24-(Phenoxyphenoxy)ethylamine and ethyl 2-(phenoxyphenoxy)ethylcarbamate are sequentially prepared in high yield and selectivity by the aminoethylation of 4-phenoxyphenol with 2-oxazolidinone under inert atomsphere, followed by amidation of 2-4-(phenoxyphenoxy)ethylamine with carbonate derivatives.
U.S. Pat. No. 6,384,280 teaches the use of 2-oxazolidinone or a derivative thereof in aminoethylation transformations involving high molecular weight polyalkylphenols to provide polyalkylphenoxyaminoalkanes of the type disclosed in U.S. Pat. Nos. 5,669,939 and 5,851,242.
Commonly assigned copending U.S. patent application Ser. No. 10/185,469, filed Jun. 28, 2002, a process for the preparation of polyalkylphenoxyaminoalkanes comprising the aminoethylation of a polyalkylphenol compound with xcex2-amino alcohol and dialkyl carbonate, which process may contain an optional alcohol.
The present invention provides an improved process for the preparation of polyalkylphenoxyaminoalkanes which comprises the aminoethylation of a polyalkylphenol compound in the presence of a basic catalyst with 2-oxazolidinone or a derivative thereof having the following formula: 
wherein R1 and R2 are independently hydrogen or lower alkyl having 1 to about 6 carbon atoms and wherein the polyalkyl group of the polyalkylphenol has an average molecular weight in the range of about 600 to 5,000 and wherein the process is carried out in the presence of an alcohol.
The alcohol has the structure R3xe2x80x94OH wherein R3 is an alkyl group having about 3 to 7 carbon atoms. The molar ratio of the alcohol to the polyalkylphenol compound is normally in the range of about 0.2:1 to 5:1.
The aminoethylation reaction of the present invention readily occurs using a basic catalyst selected from the group consisting of alkali metal lower alkoxides, alkali hydrides or alkali metal hydroxides in the temperature range of about 100xc2x0 C. to 250xc2x0 C., wherein the molar ratio of 2-oxazolidinone or a derivative thereof to polyalkylphenol compound is about 5:1 to 0.9:1 and wherein the number of equivalents of basic catalyst per equivalent of polyalkylphenol is about 0.05:1 to 1:1.
Among other things, the present invention relates to an improved process for the preparation of polyalkylphenoxyaminoalkanes in the presence of an alcohol that provides increased polyisobutylphenol conversion and reduced thermal degradation of 2-oxazolidinone in the process. Moreover, the use of an alcohol was found to mitigate the negative effect of sediment in unfiltered polyisobutylphenol (still contains salts from the neutralized alkylation catalyst) on product color. The use of polyisobutylphenol containing alkylation catalyst sediment is preferred over filtered or washed polyisobutylphenol due to process economics.
As noted above, the present invention provides an improved process for the preparation of polyalkylphenoxyaminoalkanes which comprises an aminoethylation of a polyalkylphenol compound in the presence of a basic catalyst with 2-oxazolidinone or a derivative thereof having the following formula: 
wherein R1 and R2 are independently hydrogen or lower alkyl having 1 to about 6 carbon atoms and wherein the polyalkyl group of the polyalkylphenol has an average molecular weight in the range of about 600 to 5,000 and wherein the process is carried out in the presence of an alcohol.
The reaction may be illustrated by the following: 
wherein R is a polyalkyl group having a molecular weight in the range of about 600 to 5,000, and R1, R2 and R3 are as herein described.
Prior to discussing the present invention in detail, the following terms will have the following meanings unless expressly stated to the contrary.
The term xe2x80x9calkylxe2x80x9d refers to both straight- and branched-chain alkyl groups.
The term xe2x80x9clower alkylxe2x80x9d refers to alkyl groups having 1 to about 6 carbon atoms and includes primary, secondary and tertiary alkyl groups. Typical lower alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl and the like.
The term xe2x80x9cpolyalkylxe2x80x9d refers to an alkyl group which is generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
Polyalkylphenoxyaminoalkanes may be prepared by the process of the present invention which comprises an aminoethylation of a polyalkylphenol compound with 2-oxazolidinone or a derivative thereof having the following formula: 
wherein R1 and R2 are defined herein, in the presence of a catalytic amount of an alkali metal lower alkoxide, alkali hydride or alkali metal hydroxide.
Polyalkylphenols are well known materials and are typically prepared by the alkylation of phenol with the desired polyolefin or chlorinated polyolefin. A further discussion of polyalkylphenols can be found, for example, in U.S. Pat. Nos. 4,744,921 and 5,300,701.
Accordingly, polyalkylphenols may be prepared from the corresponding olefins by conventional procedures. For example, polyalkylphenols may be prepared by reacting the appropriate olefin or olefin mixture with phenol in the presence of an alkylating catalyst at a temperature of from about 25xc2x0 C. to 150xc2x0 C., and preferably about 30xc2x0 C. to 100xc2x0 C. either neat or in an essentially inert solvent at atmospheric pressure. A preferred alkylating catalyst is boron trifluoride. Molar ratios of reactants may be used. Alternatively, molar excesses of phenol can be employed, i.e., about 2 to 3 equivalents of phenol for each equivalent of olefin with unreacted phenol recycled. The latter process maximizes monoalkylphenol.
Examples of inert solvents include heptane, benzene, toluene, chlorobenzene and 250 thinner which is a mixture of aromatics, paraffins and naphthenes. Kerosene-type jet fuel is another example of the latter mixture. Other examples of inert solvents that are aromatic mixtures include Exxon Aromatic 100, Exxon Aromatic 150, Solvesso 100, Total Solvarex 9 and the like.
The polyalkyl group on the polyalkylphenols employed in the invention is generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
The preferred polyisobutenes used to prepare the presently employed polyalkylphenols are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least about 50% and more preferably at least about 70%. Suitable polyisobutenes include those prepared using BF3 catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808. Such polyisobutenes, known as xe2x80x9creactivexe2x80x9d polyisobutenes, yield high molecular weight alcohols in which the hydroxyl group is at or near the end of the hydrocarbon chain. Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 30, a polyisobutene having a number average molecular weight of about 1,300 and a methylvinylidene content of about 74%, and Ultravis 10, a polyisobutene having a number average molecular weight of about 950 and a methylvinylidene content of about 76%, both formerly manufactured by British Petroleum. Similar polyisobutenes are currently available from BASF, ChevronTexaco, and Texas Petrochemicals.
Typically, the polyalkyl group on the polyalkylphenol has a molecular weight in the range of about 600 to 5,000, preferably about 600 to 3,000, more preferably about 700 to 3,000, and most preferably about 900 to 2,500. The polyalkyl group on the polyalkylphenol may be in any position in the phenol ring. However, substitution at the para position is preferred.
As noted above, the polyalkylphenol compound is reacted with 2-oxazolidinone or a derivative thereof having the formula illustrated herein above, wherein R1 and R2 are independently hydrogen or lower alkyl having 1 to about 6 carbon atoms. Preferably, one of R1 and R2 is hydrogen or lower alkyl of 1 to about 4 carbon atoms, and the other is hydrogen. More preferably, one of R1 and R2 is hydrogen, methyl, or ethyl, and the other is hydrogen. Still more preferably, R1 is hydrogen, methyl, or ethyl, and R2 is hydrogen. Most preferably, both R1 and R2 are hydrogen. Examples of such compounds include, but are not limited to, 2-oxazolidinone, 3-methyl-2-oxazolidinone, 4-methyl-2-oxazolidinone, and 3-ethyl-2-oxazolidinone. The 2-oxazolidinone compound is preferred. These compounds are readily commercially available. For instance, 2-oxazolidinone and 3-methyl-2-oxazolidinone may be purchased from Aldrich Chemical Company. Alternatively, these compounds may be synthesized by conventional methods apparent to the skilled artisan.
The basic catalyst employed in the process of the present invention will generally be any of the well known basic catalyst selected from the group of alkali metal lower alkoxides, alkali hydrides or alkali metal hydroxides. Typical alkali metal lower alkoxides include, but are not limited to, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium isopropoxide, potassium isopropoxide, sodium butoxide, potassium butoxide. Typically, the alkali metal lower alkoxides will contain 1 to about 6, preferably 1 to about 4, carbon atoms. Preferably, the alkali metal lower alkoxide is sodium methoxide. Sodium hydride and potassium hydride are typical alkali hydrides. Examples of alkali metal hydroxides include, but are not limited to, sodium hydroxide, lithium hydroxide, or potassium hydroxide. Sodium hydroxide and potassium hydroxide are preferred.
Typically, the reaction temperature for the aminoethylation reaction will be in the range of about 100xc2x0 C. to 250xc2x0 C., and preferably in the range of about 130xc2x0 C. to 210xc2x0 C. The reaction pressure will generally be atmospheric or lower. Lower pressures may be used to facilitate the removal of carbon dioxide. Other carbon dioxide scavengers may be employed to facilitate the reaction, such as, for example, magnesium oxide or calcium oxide.
When lower alcohols are used, it is advantageous to carry out the reaction under pressure, for example up to 100 psig depending on the alcohol, in order to raise the boiling temperature of the reaction mixture to the optimal level for the reaction. In this case, some means must be provided to remove CO2 so that carbonate salts are not formed in the reactor. This may be accomplished by controlled boiling of the reaction mixture so that solvent vapors carry the CO2 overhead into a column that condenses and recycles the solvent while venting the CO2. Nitrogen sparging into the reaction mixture or purging of the reactor head space may also be used to accomplish the same end while maintaining pressure on the reactor.
The molar ratio of 2-oxazolidinone or a derivative thereof to the polyalkylphenol compound is normally in the range of about 5:1 to 0.9:1, and preferably will be in the range of about 2:1 to 1:1. In general, the number of equivalents of the basic catalyst per equivalents of polyalkylphenol will be in the range of about 0.05:1 to 1:1, and preferably in the range of about 0.1:1 to 1:1.
The aminoethylation reaction may be carried out neat or in the presence of a solvent which is inert to the reaction of the polyalkylphenol compound and the 2-oxazolidinone or a derivative thereof. An inert solvent is often used to facilitate handling of the polyalkylphenol and to promote good contacting of the reactants. When employed, examples of inert solvents include heptane, benzene, toluene, chlorobenzene and 250 thinner which is a mixture of aromatics, paraffins and naphthenes. Kerosene-type jet fuel is another example of the latter mixture. Other examples of inert solvents that are aromatic mixtures include Exxon Aromatic 100, Exxon Aromatic 150, Solvesso 100, Total Solvarex 9 and the like. Other solvents apparent to those skilled in the art may also be used. For example, any number of ethers, aprotic polar solvents or alcohols may also be useful in the process of the present invention.
In accordance with the present invention, an alcohol is employed in the aminoethylation process. The alcohol has the structure R3xe2x80x94OH wherein R3 is an alkyl group having about 3 to 7 carbon atoms, preferably about 5 to 7 carbon atoms, most preferably about 6 carbon atoms. Examples of typical alcohols include n-propanol, n-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and mixed isomers of each of the foregoing alcohols including branched- or straight-chain alcohols. 1-Hexanol or hexanol isomers are preferred. Examples of commercial alcohols available from ExxonMobil Chemical that are a mix of several isomers include Exxal 6 (hexyl alcohol) and Exxal 7 (isoheptyl alcohol).
The molar ratio of the alcohol to the polyalkylphenol compound is normally in the range of about 0.2:1 to 5:1, preferably about 0.4:1 to 2:1, and most preferably about 0.5:1 to 1.5:1.
The aminoethylation reaction will generally be carried out over a period of about 2 to 24 hours, and preferably over a period of about 3 to 20 hours. Upon completion of the reaction, the desired polyalkyphenoxyaminoalkane is isolated using conventional techniques.